1// Copyright 2009 the V8 project authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef V8_REGEXP_REGEXP_STACK_H_
6#define V8_REGEXP_REGEXP_STACK_H_
7
8#include "src/base/logging.h"
9#include "src/base/macros.h"
10#include "src/globals.h"
11
12namespace v8 {
13namespace internal {
14
15class RegExpStack;
16
17// Maintains a per-v8thread stack area that can be used by irregexp
18// implementation for its backtracking stack.
19// Since there is only one stack area, the Irregexp implementation is not
20// re-entrant. I.e., no regular expressions may be executed in the same thread
21// during a preempted Irregexp execution.
22class RegExpStackScope {
23 public:
24  // Create and delete an instance to control the life-time of a growing stack.
25
26  // Initializes the stack memory area if necessary.
27  explicit RegExpStackScope(Isolate* isolate);
28  ~RegExpStackScope();  // Releases the stack if it has grown.
29
30  RegExpStack* stack() const { return regexp_stack_; }
31
32 private:
33  RegExpStack* regexp_stack_;
34
35  DISALLOW_COPY_AND_ASSIGN(RegExpStackScope);
36};
37
38
39class RegExpStack {
40 public:
41  // Number of allocated locations on the stack below the limit.
42  // No sequence of pushes must be longer that this without doing a stack-limit
43  // check.
44  static const int kStackLimitSlack = 32;
45
46  // Gives the top of the memory used as stack.
47  Address stack_base() {
48    DCHECK(thread_local_.memory_size_ != 0);
49    return thread_local_.memory_ + thread_local_.memory_size_;
50  }
51
52  // The total size of the memory allocated for the stack.
53  size_t stack_capacity() { return thread_local_.memory_size_; }
54
55  // If the stack pointer gets below the limit, we should react and
56  // either grow the stack or report an out-of-stack exception.
57  // There is only a limited number of locations below the stack limit,
58  // so users of the stack should check the stack limit during any
59  // sequence of pushes longer that this.
60  Address* limit_address() { return &(thread_local_.limit_); }
61
62  // Ensures that there is a memory area with at least the specified size.
63  // If passing zero, the default/minimum size buffer is allocated.
64  Address EnsureCapacity(size_t size);
65
66  // Thread local archiving.
67  static int ArchiveSpacePerThread() {
68    return static_cast<int>(sizeof(ThreadLocal));
69  }
70  char* ArchiveStack(char* to);
71  char* RestoreStack(char* from);
72  void FreeThreadResources() { thread_local_.Free(); }
73
74 private:
75  RegExpStack();
76  ~RegExpStack();
77
78  // Artificial limit used when no memory has been allocated.
79  static const uintptr_t kMemoryTop = static_cast<uintptr_t>(-1);
80
81  // Minimal size of allocated stack area.
82  static const size_t kMinimumStackSize = 1 * KB;
83
84  // Maximal size of allocated stack area.
85  static const size_t kMaximumStackSize = 64 * MB;
86
87  // Structure holding the allocated memory, size and limit.
88  struct ThreadLocal {
89    ThreadLocal() { Clear(); }
90    // If memory_size_ > 0 then memory_ must be non-NULL.
91    Address memory_;
92    size_t memory_size_;
93    Address limit_;
94    void Clear() {
95      memory_ = NULL;
96      memory_size_ = 0;
97      limit_ = reinterpret_cast<Address>(kMemoryTop);
98    }
99    void Free();
100  };
101
102  // Address of allocated memory.
103  Address memory_address() {
104    return reinterpret_cast<Address>(&thread_local_.memory_);
105  }
106
107  // Address of size of allocated memory.
108  Address memory_size_address() {
109    return reinterpret_cast<Address>(&thread_local_.memory_size_);
110  }
111
112  // Resets the buffer if it has grown beyond the default/minimum size.
113  // After this, the buffer is either the default size, or it is empty, so
114  // you have to call EnsureCapacity before using it again.
115  void Reset();
116
117  ThreadLocal thread_local_;
118  Isolate* isolate_;
119
120  friend class ExternalReference;
121  friend class Isolate;
122  friend class RegExpStackScope;
123
124  DISALLOW_COPY_AND_ASSIGN(RegExpStack);
125};
126
127}  // namespace internal
128}  // namespace v8
129
130#endif  // V8_REGEXP_REGEXP_STACK_H_
131